340 THE ADDRESSES, LECTURES, ETC., OF 



convenient, but also the cheapest form of fuel, and the enormous 

 increase of consumption, the superior quality of the illuminating 

 gas obtained by selection, and the proportionate increase of by- 

 products, would amply compensate the gas company or corporation 

 for the comparatively low price of the heating gas. 



The greater efficiency of gas as a fuel results chiefly from the 

 circumstance that a pound of gas yields in combustion 22,000 

 heat units, or exactly double the heat produced in the combustion 

 of a pound of ordinary coal. This extra heating power is due 

 partly to the freedom of the gas from earthy constituents, but 

 chiefly to the heat imparted to it in effecting its distillation. 

 Recent experiments with gas-burners have shown that in this 

 direction also there is much room for improvement. 



The amount of light given out by a gas flame depends upon the 

 temperature to which the particles of solid carbon in the flame are 

 raised, and Dr. Tyndall has shown that, of the radiant energy set 

 up in such a flame, only the T \th part is luminous ; the hot 

 products of combustion carry off at least four times as much 

 energy as is radiated, so that not more than one hundredth part 

 of the heat evolved in combustion is converted into light. This 

 proportion could be improved, however, by increasing the tem- 

 perature of combustion, which may be effected either by intensified 

 air currents or by regenerative action. Supposing that the heat 

 of the products of combustion could be communicated to metallic 

 surfaces, and be transferred by conduction or otherwise to the 

 atmospheric air supporting combustion in the flame, we should be 

 able to increase the temperature accumulatively to any point 

 within the limit of dissociation ; this limit may be fixed at about 

 2,300 C., and cannot be very much below that of the electric 

 arc. At such a temperature the proportion of luminous rays to 

 the total heat produced in combustion would certainly be more 

 than doubled, and the brilliancy of the light would at the same 

 time be greatly increased. Thus improved, gas-lighting may 

 continue its rivalry with electric lighting both as regards economy 

 and brilliancy, and such rivalry must necessarily result in great 

 public advantage. 



In the domestic grate radiant energy of inferior intensity is 

 required, and I for one do not agree with those who would like to 

 see the open fireplace of this country superseded by the continental 



